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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Respir Physiol Neurobiol. 2013 Aug 11;189(3):10.1016/j.resp.2013.07.027. doi: 10.1016/j.resp.2013.07.027

Figure 4.

Figure 4

Preprocessing steps for Watershed segmentation. Coronal crosssection of a left-lobe showing the aerosol fluorescent image after different preprocessing steps. a - initial fluorescent aerosol image reconstructed from transverse images. b – after processing with high-pass filter to reduce the low frequency gray value variations. c – following median filter to suppress small bright gray-value peaks. d – application of low-pass filter to prevent over segmentation. e – overlay of lobe boundary to constrain segmentation within lobes.